Compressor throttling apparatus



Filed Sept. 29, 1942 my N INVENTOR Eums E.Hew1it BY s H 7 ATTORNEY Patented Aug. 21, 1945 UNITED PATENT OFFICE.

X I 2,383,250 a COMPRESSOR THROTTLING APPARATUS El lis'E. Hewitt, Edgewo od, Pa, assignor to The Westinghouse Air Brake Company, Wilmerding,

,P a,, a, corporation of Pennsylvania Application September 29, 19.42, Serial No. 460,131

4 Claims. c1. zen-P2 more particularlyto a discharge throttling valve.

compressor operating undervarying loadTconditions, such as a steam driven compressor of the type employed in rail-way air brake service it has been proposed to provide means responsive to the receiving reservoir "pressure for controlling the supply of steam or other motive power to the compressor. One "form of compressor steam throttling valve device in common use, for example; is arranged to reduce the flow of the steam tothe-compressor while the pressure of air in the receiving reservoir is too low to provide an adequate cushion for the'air pistons of the compressor, thus preventing damage to the pistons and cylinder heads, breakage of reversing valve rods, and other ill effects produced by racing of a cornpres/sor; of this type have proved satisfactoryunder favorable operating conditions, the construction of the necessarily complicated operating elements thereof involves expense and the use of scarce strategic materials; so that economical production of valves of this classmay be difficult. Further.-

' more, a steam throttling valve is sometimes rendered inoperative in railway service because of salts and limes precipitated out of the steam when bad .water is encountered.

. It isone objectof my invention to provide a novel fluid throttle arrangement ofsimple and in.- expensive construction, which may be dispose in the .air discharge line of a compressor for produc: ing a proper cushioning effect upon the compress sor to prevent racing, and which is not subject to the undesirable features of the steam throttlin valve just mentioned.

Another object Iof the invention is toprovide a .novel discharge throttling valve arrangement which mayform an integral part ofa complete compressor of the type useful in railway sel'vi qe.

' Other. objectsand advantages of the invention Although steam throttling valve devices videcl a'fluid compressor, indicated generally by the reference numeral 5, which may be of the steam .d-riven type and comprises a cylinder 5 having a. compression chamber 1 in which is mounted a piston 8, which'is arranged for operationthrough the medium of a piston rod 9 by a steam actuated piston, not illustrated. It will be understood that suitable inletva-lves, not shown, are provided foradmitting air to the compression chamber below the piston 8' at the start of its downward stroke, and above the piston upon initial upward movement thereof, so thatthe piston is adapted to compress air upon movement in either direction.

Formed in a lateral extensionoi the cylinder 6 are upper :and lower valve chambers H and I2, which communicate with the compression cham her 7 'by wayof .ports 13 and,respectively, and which are also connected to a common discharge passageway t6. -Mounted in the valve chamber II is a normally seated check valve element H which is arrangedto preventrbackfiow of air from passageway L6 to .the compression chamber. A similar check valve element I 8 isdisposed in the valve chamber 12 for the samepurpose;

According to the invention as disclosed in Fig. 1, there is provided a discharge throttle valve .device zllwcomprisinga casing structure 2A which is Carried .by the compressor cylinder .61 and which has formed therein a valve chamber 22,. and a chamber 23 separated therefrom .by a wal1w24.

The valve chamber 22 is connectedby way of a pipe .41! $0 a receiving reservoir .42, The chamber 23 is always in communication with the passagewill appear in the following more detailed description thereof, taken in connection with accompanying drawing, wherein Fig. 1 isua diagrammatic sectional view or a portion of a compressor apparatus having the throttling valve mechan sm a sqciated t er with; and

r Fig. 2 is a similarvi w n vhichazmod tl dzfqr ofthrottling va -vemechanism illu t a ed.-

ails shown in Fig. 1 of the drawing, there is prowaylfi of the compressor by way of an opening 26, and communicates with thevalve chamber 22 through a restricted port 21, and also by way of a bore 28, both formed in the wall 24 Disposed in the valve chamberEZ-is a valve element 39, which is adapted to engage a seat 3| formed at the upper endof the bore 28, and which has several lugs 32 slidably engaging the bore; A plunger 35 slidablymou-nted in a bore 36 in the casing structure 2| is provided for biasing valve element =30 toward seated position, the pressure areaof the plunger being'preferably greaterthan that of the undersidexof the valve element 30 within the bore 28. The plunger -35 is subjectto the pressure of air in the chamber 22, and'has a boss 3?! which is operatively engageable with the. upper surface of the valve element 30 under the force exerted by a coil spring .38, that is interposed between the 'plungerizand a cover. element 3fl having screwthreaded engagement with thexcasing structure 21.. "The cover element 39 isprovided with an open port 40 for venting the space at the upper side of the plunger 35.

In operation, the compressor piston 8 is reciprocated in the usual manner for compressing air in the compression chamber 1, the air being forced past the respective check valves I! and. 8 to the discharge passageway 6. Assuming that the pressure of air in the reservoir 42 is initially below that providing'the desired cushioning effect for the compressor, the force exerted by the spring 38 against the plunger 35 remains effective to hold the valve element 30 on the seat 3|, so that the flowof compressed air from the passageway l6 and the chamber 23 is confined to the restricted port 21, from, which the air flows through the valve chamber 22 and pipe 4| to the reservoir 42.

With the check valve 30 thus held in seated position, only a portion of the compressed air supplied to the discharge passageway l6 and chamber 23 can flow therefrom to the reservoir, because of the limited flow area of therestricted port 21, and as a result a back pressure is created for cushioning the compressor piston 8 and preventing racing of the compressor. It will thus in seated position, the air pressure in chamber. 23 must exceed that in valve chamber 22, by reason of the retardation of the flow of air through the restricted port 21 on its way to the reservoir.

After the compressor has been operated for a sufliciently long interval to cause the total effective pressure of air acting upwardly on the valve element 30 and plunger 35 to exert a predetermined critical force of approximately fiftyfive pounds against the spring 38, the downward force of the spring is overcome 'to permit initial upward movement of thevalve element 30 away from the seat 3|. The higher pressure of air existing in the chamber 23 then becomes effective overthe larger areaof the plunger 35, which is thereby quickly raised to its uppermost position to permit further upward movement of the valve element 30 with a snap action.

So long as the reservoir pressure acting against the plunger 35 remains above the predetermined critical value, as determined bythe force exerted by the spring 38, the plunger is held in its uppermost position, and the valve element 3|]- will not be subjected to any biasing force other than that of its own weight. The full capacity of the compressor 5 is then available '25 be evident that while valve element remains 40 under this condition is thus permitted to flow for maintaining the desired pressure of air in the reservoir 42.

Embodiment shown in Figure 2 In Fig. 2 of the drawing there is shown a compressor throttle valve apparatus constructed in accordance with a modified form of the invention, the various associated elements, including the compressor 5 and reservoir 42, being similar to those described in connection with Fig.- 1. For insuring the desired back pressure. in the compressor discharge passageway [6 there is provided a throttle valve device 50 comprising a casing structure 5|, carried by the compressor.

of the casing structure separating the chamber 52 from the valve chamber 54.

Interposedbetween the casing structure 5| and the casing section 56 is a flexible diaphragm 60, on the upper side of which is disposed a follower member 62, and on the lower side of which is provided a valve element 63 having a threaded stem 64 inserted through suitable apertures in the diaphragm and follower member for receiving an assembly nut 65. The valve element 63 is adapted to engage a valve seat 64 for controlling communication between the chamber 52 and valve chamber 54, it being noted that the area of the valve element exposed to the chamber 52, when the valve is in seated position as shown in the drawing, is less than the area of the diaphragm 60 subject to fluid pressure in the valve chamber 54. A coil spring 61 is interposed between the follower member 62 and a plug 68 having screw-threaded connection with' the casing section 56 for providing a predetermined biasing force urging thevalve element 63 against the seat 64. therein an atmospheric exhaustpassage 69 for venting the spring chamber55. v a

The principle of operation of the throttle valve device 50 will be understood from the explanation hereinbefore presented in connection with Fig. 1. When the compressor 5 is operated to supply compressed air to the reservoir 42 while the fluid pressure therein is insufiicient to provide the desired backpressure for preventing pounding of the compressor piston 8,; the valve element 63 remains in engagement with the seat 64 under thepressure of; the-spring 61, which is effective to prevent flexing --of the diaphragm 60 as long as the pressure of airyin the chamber 54 is less than a predetermined critical pressure. Air compressed by the pistont from the chamber 52 to the reservoir only by way of the restricted port 58, and the resultantback pressure becomes 'eflective tocushion the? compressor piston 8. When the reservoir pres-' sure has been built up sufiiciently tocooperatewith the pressure of air in the chamber 52 for unseating the valve element 63, that element the unseating movement 'of the valve element 63' is effected suddenly, by reason of the additional area of the diaphragm v6|! thatis subjected .to the pressure of air from the chamber 52. after the valve element is initially moved away from its seat. i It will now be apparent that either of the. two preferred embodiments of theinve'ntion' may be utilized for throttling the flow, of air compressed by a compressor to cushion the operation thereof, until the pressure of air in the receiving reservoir has been increased to a predetermined value, and that automatic regulation of the compressor will thereby be provided throughout a normalservice life at minimum cost and without creating additional burdens of inspection and repair. I I

Having now described my invention, what I claim as new and desire to secure by Letters Patent is: I

1. In an apparatus of the class described including a compressor anda reservoir, in'combination, a throttling valve device comprising casing means including a wall interposed in the ,communication between the outlet of said compressor The plug 68 has formed and said'reservoir, said .wall having an alwaysopen restricted passage, and -.valve means. con.-

' trolling an additional communication of larger bination therewithof a' throttling valve device comprisingbiasin vnieans; and valve means subject to the opposing pressures of said biasing means and of fluid flowing from said compressor to said. reservoir, saidvalve means being constructed and arranged to controltlie rate of such flow of fluid under. pressure, thereby to main- .a back pressure cushioning operation of the compressor.

3.:In an equipment of theclass described includi-ng a tcompressorand a reservoir, the combination therewith of :a throttling valve device comprising a spring, valve means subject to the opposing forces of said spring andlof. fluid under pressure supplied by said compressor to said reservoir, said valveflmeans ibeing interposed in the discharge.

communication of said compressor for so controlling the rate of flow of fluid therethrough as r to maintain a back pressure cushioning operation of said compressor, and a restricted by ass communication through which fluid under pressure may at any time be supplied from said compressor to said reservoir.

4. In combination, a compressor of the pressure motor actuated type having a discharge passage, a reservoir ior receiving fluid under pressure delivered by said compressor at said discharge passage, and a throttle valve device interposed between said compressor discharge passage and said reservoir, comprising valve means operative when a reservoir for receiving fluid under pressure delivered by said compressor at said discharge passage, anda throttle valve device interposed between said compressor discharge passage and said reservoir comprising a valve element adapted to seat against the pressure of fluid in said discharge passage to cut off all but a restricted flow of fluid therefrom to said reservoir, a spring, and movable abutment means through which said spring acts to urge said valve means toward seated position, said movable abutment means being subject to the pressure of fluid in said reservoir and operative upon a predetermined increase in reservoir pressure to counteract the force of said spring.

6. The combination with a compressor having a discharge passage and a reservoir for receiving fluid under pressure delivered by said compressor at said discharge passage, of a throttle valve device interposed between said compressor discharge passage and said reservoir, comprising snap acting valve means controlling a communication through which fluid under pressure flows from said discharge passage to said reservoir, said M valve means being subject to the pressure of fluid in said reservoir, and means constituting an always-open restricted communication through which fluid under pressure may at all times flow from said compressor discharge passage to said reservoir.

7. The combination with a compressor having described including a compressor and a reservoir, in combination, a casing having an inlet chamber a discharge passage .and a reservoir for receiving fluidunder pressure delivered'by said compressor at said-discharge passage, of a :throttle valve. device interposed between said compressor discharge passage and said reservoir, comprising valve means having a pressure area subject to the pressureof fluid in said discharge passage, said valve means "being operative when seated. to cut off .all but a restricted 'fiowof fluid to said reservoinand spring-pressed movable abutment means constructedand arranged to bias'saidvalve means toward seated position, said movable abutment pair lofcheck valve devices controlling communication betweenathe respective fluid discharge ports of the compressor :and a common discharge pas sageway; a receiving reservoir, and throttle valve means interposed. in 2. communication between said discharge passageway and said reservoir, said throttle valve .means lbeing operative to restrict flowlofffluid under pressure through said communication unlessthe pressure oifluid in said reservoir exceeds a predetermined value. v

9. In a fluid pressure apparatus of the class described including a compressor and a reservoir, in combination, a casing having an inlet chamber to which fluid under pressure is'delivered bythe compressor and an outlet chamber communicating with said reservoir, a valve element controlling all but a restricted flow of fluid under pressure from said inlet chamber to said outlet chamber, and a spring-pressed piston normally biasing said valve toward seated position and subject to the opposing pressure of fluid in said outlet chamber. I

10. The combination with a fluid compressor of the pressure motor actuated type, and a receiving reservoir, of a discharge throttle valve device comprising a casing carried by said compressor and having an inlet chamber to which fluid under pressure is initially delivered thereby and an outlet chamber communicating with said reservoir, a wall separating said chamber and having large and small ports, a valve controlling said large port, adjustable spring means, and a plunger engageable with said valve and subject to the opposing pressures of said spring and of fluid in said outlet chamber. j

11. In a fluid compressor equipment of the class to which fluid under pressure is delivered by the compressor and an outlet chamber communicating with said reservoir, a valve element controlling all but a restricted flow of fluid under pressure from said inlet chamber to said outlet chamber, a spring for normally biasing said valve toward seated position, and a diaphragm interposed I a between said spring and said valve and subject to the pressure of fluid in said outlet chamber.

reservoir, means providing an always-open re stricted communication between said chambers, a valve controlling a larger communication between said chambers, adjustable spring means,

and a diaphragm cooperative with said valve and subject to the opposing pressures of said spring means and of fluid in said outlet chamber;

13. In a steam driven compressor including an air compression cylinder and a piston operatively mounted therein, the combination therewith .of a throttling valve device comprising a casing having a discharge chamber to which compressed air can flow from said cylinder, a receiving chamber communicating with said discharge chamber through an always open port and also through a' larger valve opening, and a spring chamber open to atmosphere, a valve constructed and arranged to be .seated for closing said larger opening against the pressure of air in'said discharge chamber, a, movable abutment interposed between said receiving cnamber and said spring chamber, said movable abutment being cooperative with said valve, and an adjustable spring constructed and arranged in said spring chamber to act on said movable abutment forv urging said valve toward seated position, whereby said valve is operable to restrict flow of air from said compression cylinder until back pressure is established in said receiving chamber for'cushioning compression strokes of said piston.

14. In a steam driven compressor of the class including an air compression cylinder having a dischargemanifold, a double acting piston reciprocatively mounted in said cylinder, and check valves interposed between each end of said cylinder and said discharge manifold, the combination therewith of a valve casing carried by said cylinder and having a discharge chamber communicating with said discharge manifold, a receiving chamber communicating with said-discharge chamber through an always open port and also through a larger valve opening, and a spring chamber open to atmospherea valve constructed and arranged for closing said larger opening againist the pressure of air in said discharge chamber, a movable abutment interposed between exerted by said spring.

ELLIS E. HEWITT. 

